Object-oriented method and apparatus for rendering a 3D surface image on a two-dimensional display

• US 5,729,671 A
• Filed: 03/08/1996
• Issued: 03/17/1998
• Est. Priority Date: 07/27/1993
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Object Technology Licensing Corporation
• Inventors: Jain, Rajiv, Peterson, John
• Primary Examiner(s): Zimmerman, Mark K.
• Application Number:
  US08/612,675
• Time in Patent Office: 739 Days
• Field of Search: 395/162, 395/121, 395/123, 395/133, 395/134, 395/522
• US Class Current: 345/423
• CPC Class Codes: G06T 15/80 Shading

Abstract

A method and system provides an object-oriented framework for rendering three-dimensional surfaces on a two-dimensional display in a flexible manner. The framework comprises two main classes that work together to render discretized data points that represent the three-dimensional graphic objects. The first class is used to construct a surface object which has a first member function that generates vertex information for each of the data points and stores the vertex information in a memory. The surface object also contains a second member function which generates indices into the stored vertex information which indices define shards on the surface which is being rendered. The second class is used to construct a rendering object which calls the first and second member functions in the surface object to first process the vertex data for display and then use the shard indices to retrieve the processed vertex data to render the surface. Vertex data processing is separated from shard processing to increase the efficiency of the rendering process.

Claims

1. In a computer having a memory and a 2D display, a system for rendering on the display an image of a 3D surface, the image being defined by point data stored in the memory, the system comprising:

(a) subclassable surface object class information, stored in the memory and having segment data logic for generating vertices data from stored point data and for storing the vertices data in the memory, and shard iteration logic for generating a plurality of indices into the stored vertices data, the plurality of indices selecting three vertices defining a shard;

(b) surface object means for constructing a plurality of 3D surface objects from the surface object class information, each surface object corresponding to a chunk of the 3D surface image, each chunk defined by a plurality of shards, wherein each surface object includes means for invoking shard iteration logic peculiar to the surface object class from which it was constructed; and

(c) a rendering object, stored in the memory and having

first means for iterating over the surface objects to select one surface object corresponding to a chunk to be rendered, the first means including means for generating a block of vertices data corresponding to the selected surface object,

second means for generating 2D display data from the vertices data, third means for invoking the shard iteration logic to retrieve indices defining the plurality of shards for the selected surface image chunk, and fourth means for rendering the shards defining the chunk on the display using the 2D display data and the retrieved shard indices.

2. The system of claim 1 wherein the segment data logic includes a segment iterator object having a member function for sequentially generating vertices data representing points on a target surface segment from stored point data, and wherein the shard iteration logic includes a shard iterator object having a member function that generates indices into the stored vertices data defining a plurality of shards which form the target image segment.

3. The system of claim 2 wherein the second means includes means for transforming the stored vertices data into the 2D display data, and wherein the fourth means uses the retrieved shard indices to retrieve the stored transformed vertices data and provide it to the rendering means.

4. The system of claim 1 wherein the vertices data includes at least one of the group consisting of:

normal and shading values for each vertex;

color information for each vertex;

texture map information for each vertex; and

shading information for each vertex.

5. The system of claim 1 wherein the shard iteration logic includes means for generating visibility flag information indicating when an edge of one of the shards is visible;

and wherein the rendering means includes means responsive to the visibility flag information for rendering the edge.

6. The system of claim 5 further including means for providing clipping information to the shard iteration logic and wherein the visibility flag information generating means is responsive to the clipping information for generating the visibility flag information.

7. The system of claim 6 wherein the system further includes means for providing backfacing information to the shard iteration logic and wherein the visibility flag information generating means is responsive to the backfacing information for generating the visibility flag information.

8. In a computer having a memory and a 2D display, a method for rendering on the display an image of a 3D surface, the image being comprised of an image surface segment defined by point data stored in the memory, the method comprising the steps of:

(a) storing in the memory subclassable surface object class information having segment data logic for generating vertices data from stored point data and for storing the vertices data in the memory, and shard iteration logic for generating a plurality of indices into the stored vertices data, the plurality of indices selecting three vertices defining a shard;

(b) constructing a plurality of 3D surface objects from the surface object class information, each surface object corresponding to a chunk of the 3D surface image, each chunk defined by a plurality of shards, wherein each surface object includes means for invoking shard iteration logic peculiar to the surface object class from which it was constructed;

(c) constructing a rendering object in the memory;

(d) using the rendering object to select one surface object corresponding to a chunk to be rendered and to invoke the 3D surface object to generate and store vertices data corresponding to the selected surface object;

(e) using the rendering object to generate 2D display data from the vertices data;

(f) using the rendering object to invoke the shard iteration logic to retrieve indices defining the plurality of shards for the selected surface image chunk; and

(g) using the rendering object to render the shards defining the chunk on the display using the 2D display data and the retrieved shard indices.

9. The method of claim 8 wherein the segment data logic includes a segment iterator object having a member function for sequentially generating vertices data representing points on a target surface segment from stored point data, and wherein the shard iteration logic includes a shard iterator object having a member function that generates indices into the stored vertices data defining a plurality of shards which form the target image segment.

10. The method of claim 9 wherein step (e) comprises the steps of:

(e1) transforming the stored vertices data into the 2D display data, and wherein step (g) comprises the steps of;

(g1) using the retrieved shard indices to retrieve the stored transformed vertices data.

11. The method of claim 8 wherein the vertices data includes at least one of the group consisting of:

normal and shading values for each vertex;

color information for each vertex;

texture map information for each vertex; and

shading information for each vertex.

12. The method of claim 8 wherein the shard iteration logic includes logic for generating visibility flag information indicating when an edge of one of the shards is visible;

and wherein step (g) comprises the step of;

(g1) using the visibility flag information to render the edge.

13. The method of claim 12 further including the step of:

(h) providing clipping information to the shard iteration means and wherein the visibility flag information generating means is responsive to the clipping information for generating the visibility flag information.

14. The method of claim 12 further including the step of:

(l) providing backfacing information to the shard iteration means and wherein the visibility flag information generating means is responsive to the backfacing information for generating the visibility flag information.

15. A computer program product for use in a computer having a memory and a 2D display, a system for rendering on the display an image of a 3D surface, the image being defined by point data stored in the memory, the computer program product comprising a computer usable medium having computer readable program code thereon including:

(a) surface object class code having segment data logic for generating vertices data from stored point data and for storing the vertices data in the memory, and shard iteration logic for generating a plurality of indices into the stored vertices data, the plurality of indices selecting three vertices defining a shard;

(b) program code for constructing a plurality of 3D surface objects in the memory from the surface object class information, each surface object corresponding to a chunk of the 3D surface image, each chunk defined by a plurality of shards, wherein each surface object includes program code for invoking shard iteration logic peculiar to the surface object class from which it was constructed; and

(c) program code for instantiating a rendering object in the memory, the rendering object having

program code for iterating over the surface objects to select one surface object corresponding to a chunk to be rendered, the iterating program code including program code for generating a block of vertices data corresponding to the selected surface object,

program code for generating 2D display data from the vertices data,

program code for invoking the shard iteration logic to retrieve indices defining the plurality of shards for the selected surface image chunk, and

program code for rendering the shards defining the chunk on the display using the 2D display data and the retrieved shard indices.

16. The computer program product of claim 15 wherein the segment data logic includes a segment iterator object having a member function for sequentially generating vertices data representing points on a target surface segment from stored point data, and wherein the shard iteration logic includes a shard iterator object having a member function that generates indices into the stored vertices data defining a plurality of shards which form the target image segment.

17. The computer program product of claim 16 wherein the program code for generating 2D display data includes program code for transforming the stored vertices data into the 2D display data, and wherein the program code for rendering the shards uses the retrieved shard indices to retrieve the stored transformed vertices data and provide it to the rendering program code.

18. The computer program product of claim 15 wherein the vertices data includes at least one of the group consisting of:

normal and shading values for each vertex;

color information for each vertex;

texture map information for each vertex; and

shading information for each vertex.

19. The computer program product of claim 15 wherein the shard iteration logic includes program code for generating visibility flag information indicating when an edge of one of the shards is visible;

and wherein the program code for rendering the shards includes program code responsive to the visibility flag information for rendering the edge.

20. The computer program product of claim 19 further including program code for providing clipping information to the shard iteration logic and wherein the visibility flag information generating program code is responsive to the clipping information for generating the visibility flag information.

21. The computer program product of claim 20 further including program code for providing backfacing information to the shard iteration logic and wherein the visibility flag information generating program code is responsive to the backfacing information for generating the visibility flag information.